Reversible guideless rolling mill

ABSTRACT

A pair of rolling machines are arranged in series in alignment with a pass line along which a workpiece to be rolled is passed. The center distance between the first rolls of the first rolling machine and second rolls of the second rolling machine is designed to be not more than 1.5 times the roll diameter. The rotational axes of the first rolls are displaced by an angle of 90° from those of the second rolls and are inclined at an angle of 45° respectively with respect to the horizontal plane. A plurality of dual-purpose calibers are defined between the rolls of the rolling machines to be arranged in the axial direction, respectively. The rolls are shifted in crossing directions to the pass line respectively so as to bring desired dual-purpose calibers in alignment with the pass line.

FIELD OF THE INVENTION

[0001] The present invention relates to a reversible guideless rolling mill, more specifically to a reversible guideless rolling mill which rolls a workpiece to be rolled to a desired cross-sectional profile while the workpiece is reciprocated along a pass line.

DESCRIPTION OF THE RELATED ART

[0002] There is known a reverse type rolling mill as a mechanism for rolling a long workpiece to be rolled such as a steel bar and a wire rod to a predetermined cross-sectional profile. This reverse type rolling mill has a pair of rolling machines arranged in series in alignment with a pass line along which workpieces are fed. One rolling machine rotatably supports a pair of horizontal rolls, and the other rolling machine rotatably supports a pair of vertical rolls. The pairs of rolls in the former and latter rolling machines each define a plurality of rolling passes (calibers) arranged at predetermined intervals in the axial direction in accordance with a required pass schedule. Desired rolling passes in two pairs of rolls are designed to be aligned with the pass line by shifting these two pairs of rolls in the directions orthogonal to the pass line, respectively.

[0003] Said reverse type rolling mill is designed to carry out rolling treatments successively: A workpiece to be rolled is first rolled by passing it successively through predetermined rolling passes defined by a pair of rolls arranged in the respective rolling machines, and then the rolls are shifted so that next predetermined rolling passes are aligned with the pass line respectively. The workpiece is then fed again through the thus selected rolling passes successively in the opposite direction. That is, the reverse type rolling mill can achieve rolling of a workpiece to a predetermined cross-sectional profile by reciprocating the workpiece along a predetermined pass line.

[0004] Referring to the rolling passes to be defined between the rolls, oval calibers and round calibers are arranged alternately in the axial direction, so that a workpiece having been rolled to an oval cross section after passing through an oval caliber of one rolling machine is designed to be fed through a round caliber of the other rolling machine to a round cross section. Meanwhile, in order to guide the workpiece rolled through the oval caliber into the round caliber in an accurate orientation, a workpiece holding guide is interposed between the rolling machines. The holding guide is composed of rollers and the like. Further, it is essential to install, in each rolling machine, a screw down device for adjusting the clearance between the opposing rolls so as to change the cross-sectional dimension of the workpiece. This screw down device is designed to bring one roll closer to or farther from the other roll which is arranged in a certain fixed position. In other words, a stand supporting rotatably one roll in a housing is shiftably provided, and the stand is shifted by a suitable driving mechanism so as to adjust the roll clearance.

[0005] When the clearance between the rolls is adjusted by the screw down device incorporated into the rolling machine, the holding guide attached to the reverse type rolling mill needs adjustment to a proper position accordingly, so that a longer time is disadvantageously required for adjustment in accordance with the order change and the like. Since guiding failure of the holding guide causes defective rolled products, it is essential to carry out frequent maintenance of bearings, inspection of roll surface flaws, inspection of rotational condition of the rolls, etc. It can also be pointed out that the holding guide interposed between the rolling machines increases the total length of the rolling mill, makes the structure of the mill complicated and requires an extra cost of equipment.

[0006] As described above, since rolling passes to be defined between each pair of rolls are oval-round calibers or rhombic-square calibers designed based on a predetermined pass schedule, the size range of workpieces to be rolled by the same rolls becomes inevitably to be narrow. Therefore, in order to achieve rolling of workpieces over a wider size range, many sets of rolls matching the respective sizes must be prepared. This disadvantageously incurs cost increase and troublesome maintenance of the rolls.

SUMMARY OF THE INVENTION

[0007] In view of the problems described above, this invention is proposed to solve said subject suitably and has its object to provide a reversible guideless rolling mill which eliminates the workpiece holding guide and achieves saving of time required for order changes.

[0008] In order to solve the problems described above and attain the intended objective suitably, the reversible guideless rolling mill according to the present invention is for rolling a workpiece to be rolled into a required cross-sectional profile while the workpiece is reciprocated along a pass line; wherein two rolling machines each having a pair of rolls which defines a plurality of calibers in axial direction for rolling said workpiece are arranged in series along said pass line of the workpiece so as to establish a center distance between the rolls in one rolling machine and the rolls in the other rolling machine to be no more than 1.5 times a roll diameter; rotational axes of the rolls in one rolling machine are displaced by almost right angle from that of the rolls in the other rolling machine; and the rolls in said two rolling machines are designed to be shifted in crossing directions to the pass line of the workpiece so that each caliber is aligned with said pass line.

[0009] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings illustrated by way of examples the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention together with the objects and advantages thereof, may well be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0011]FIG. 1 is a cross-sectional view of the reversible guideless rolling mill according to a preferred embodiment of the present invention, showing a state where the mill is cut along the axis of a first roll;

[0012]FIG. 2 is a cross-sectional view of a first rolling machine according to the embodiment cut orthogonal to the axis of the first roll;

[0013]FIG. 3 is a schematic back view of the first rolling machine and a driving system according to the above embodiment;

[0014]FIG. 4 is a schematic back view of a second rolling machine and a driving system according to the above embodiment;

[0015]FIG. 5 is a schematic plan view of the driving systems of the rolling machines in the rolling mill according to the above embodiment;

[0016] FIGS. 6(a) and 6(b) are explanatory drawings showing essentially dual-purpose calibers defined between the first rolls and those between the second rolls, respectively, in the above embodiment;

[0017] FIGS. 7(a) and 7(b) are explanatory drawings showing essentially oval-round calibers defined between the first rolls and those between the second rolls, respectively, as another example;

[0018] FIGS. 8(a) and 8(b) are explanatory drawings showing essentially rhombic-square calibers defined between the first rolls and those between the second rolls, respectively, as another example;

[0019]FIG. 9 is a schematic structural view showing a line of guideless rolling mills of a preferred embodiment according to another aspect of the present invention;

[0020]FIG. 10 is a cross-sectional view of the rolling mill according to the above embodiment cut along the axis of a first roll;

[0021]FIG. 11 is a cross-sectional view of a first rolling machine according to the above embodiment cut orthogonal to the axis of the first roll;

[0022]FIG. 12 is a schematic back view of the first rolling machine and a driving system according to the above embodiment;

[0023]FIG. 13 is a schematic back view of a second rolling machine and a driving system according to the above embodiment; and

[0024]FIG. 14 is a schematic plan view of the driving systems of the rolling machines in the rolling mill according to the above embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0025] The reversible guideless rolling mill according to the present invention will be described by way of a preferred embodiment referring to the attached drawings.

[0026] As shown in FIG. 1, a reversible guideless rolling mill 10 (hereinafter also referred simply to as a rolling mill) is composed essentially of two rolling machines 12 and 13 arranged in series in alignment with a pass line PL along which workpieces 11 to be rolled are fed. Further, roller tables 14, each having a multiplicity of rollers arranged rotatably at predetermined intervals, are disposed on the upstream side and downstream side of the rolling mill 10 with respect to the machine direction (see FIG. 5), and a workpiece 11 loaded on the table 14 is designed to be reciprocated as such with respect to the rolling mill 10.

[0027] One rolling machine (first rolling machine) 12 constituting the rolling mill 10 has a pair of first rolls 17 opposing each other across the pass line PL. The first rolls 17 are supported rotatably in a first stand 16 incorporated to a housing 15 of the mill 10. Meanwhile, the other rolling machine (second rolling machine) 13 has a pair of second rolls 19 opposing each other across the pass line PL. The second rolls 19 are supported rotatably in a second stand 18 incorporated to the housing 15 of the mill 10. The rotational axes of the first rolls 17 in the first rolling machine 12 are arranged to displace at an angle of 90° from those of the second rolls 19 in the second rolling machine 13, and the first rolls 17 and the second rolls 19 are oriented such that the rotational axes of the former and those of the latter are inclined at an angle of 45° (X orientation) respectively with respect to a horizontal plane (see FIGS. 3 and 4). Be noted here, on the basis, for example, of the first rolls 17 disposed in the first rolling machine (one rolling machine) 12, while the inclination angle of the rotational axis of each roll 17 with respect to the horizontal plane is not limited to 45° but may be within the range of 20 to 90°, it is most preferably 45°.

[0028] The first stand 16 is designed to be movable with respect to the housing 15 in a direction orthogonal to the pass line PL and also to be shifted by a predetermined pitch by first hydraulic cylinders 20 serving as driving means, as shown in FIG. 3. As shown in FIG. 6(a), the pair of first rolls 17 disposed in the first stand 16 define therebetween a predetermined number of first dual-purpose rolling passes (calibers) 21 arranged in the axial direction, which can serve both as oval calibers and round calibers. The first stand 16 is designed to shift by the pitch that brings the center of a desired caliber in alignment with the pass line PL.

[0029] The second stand 18 is designed to be movable with respect to the housing 15 in a direction orthogonal to the pass line PL and to the shifting direction of the first stand 16 and also to be shifted by a predetermined pitch by second hydraulic cylinders 22 serving as driving means. As shown in FIG. 6(b), the pair of second rolls 19 disposed in the second stand 18 define therebetween a predetermined number of second dual-purpose rolling passes (calibers) 23 arranged in the axial direction, which can serve both as oval calibers and round calibers. The second stand 18 is designed to shift by the pitch that brings the center of a desired caliber in alignment with the pass line PL like in the first stand 16.

[0030] The dual-purpose calibers 21 and 23 are formed to be able to serve both as oval calibers and round calibers by adjustment of the clearance between the pair of rolls 17 and that between the pair of rolls 19. In this embodiment, the diameters of the calibers are designed to reduce gradually from one side to the other side of the rolls in the axial directions. A workpiece 11 is designed to be rolled to have a predetermined cross-sectional profile by passing it alternately through the dual-purpose caliber 21 or 23 preset to serve as an oval caliber and then through the dual-purpose caliber 23 or 21 preset to serve as a round caliber. In the advancing stroke and retracting stroke of the workpiece 11, the caliber through which the workpiece 11 is passed first is designed to be oval, and the caliber through which the workpiece 11 is passed next is designed to be round. While the feeding direction of the workpiece 11 passed through the rolling mill 10 is inverted, the workpiece 11 is designed to be fed back as such to the rolling machines 13 and 12 in the rolling mill 10 without turning the workpiece 11 in the radial direction.

[0031] The center distance P between the first rolls 17 in the first rolling machine 12 and the second rolls 19 in the second rolling machine 13 is preset to be not more than 1.5 times the diameter R of the rolls 17(19), as shown in FIG. 1. By reducing the center distance P between the rolls 17 and the rolls 19 arranged adjacent to each other along the pass line as described above, the workpiece 11 rolled first in a dual-purpose caliber 21 or 23 of one rolling machine 12 or 13 can be guided accurately to a dual-purpose caliber 23 or 21 of the other rolling machine 13 or 12 through which the workpiece 11 is rolled next without interposing a workpiece holding guide between these two rolling machines 12 and 13. That is, operations of adjusting and inspecting the holding guide required in accordance with an order change can be omitted, and occurrence of defective products attributed to the presence of the holding guide can be eliminated. Further, the absence of the holding guide can reduce the total length of the rolling mill.

[0032] It should be noted here that the center distance P between the opposing rolls 17 and 19 can be reduced by employing a mechanism (to be described later) as a screw down device for adjusting the clearance between the opposing rolls 17(19). Therefore, the constitutions of the rolling machines 12 and 13 will be described. Here, since the first rolling machine 12 and the second rolling machine 13 are of the same constitution, except that the rotational axes of the rolls 17 are displaced by an angle of 90° from those of the rolls 19, the constitution of the first rolling machine 12 only will be described. The same elements in the second rolling machine 13 as in the first rolling machine 12 are affixed with the same reference numbers respectively, and detailed description of them will be omitted. The rolling machines are not to be limited to the eccentric type rolling machines, but the present invention can be applied to chock type rolling machines. However, eccentric rolling machines are given as an example in the following embodiments.

[0033] The first stand 16 disposed in the housing 15 of the rolling mill 10 contains two pairs of through holes 24 defined in a direction orthogonal to the pass line PL, each pair containing an upper through hole 24 and a lower through hole 24. That is, four through holes 24 are defined in the first stand at inner positions (closer to the opposing sides of the rolling machines 12 and 13) on each side of the workpiece pass line PL and at an upper position and a lower position, respectively. An eccentric sleeve 25 is fitted rotatably in each through hole 24, and the sleeve 25 contains an eccentric through hole 25 a having an axis offset from that of the through hole 24. A roll shaft 26 is inserted to the upper and lower eccentric through holes 25 a and are born thereby rotatably through bearings 27. Meanwhile, the roll shafts 26 have the first rolls 17 fitted thereon between the eccentric sleeves 25 to be rotatable integrally with the shaft 26. The workpiece 11 is designed to be rolled by passing it through a first dual-purpose caliber 21 defined by the pair of first rolls 17 arranged in a diagonally vertical relationship. The axis C₁ of each roll shaft 26, inserted to the eccentric through holes 25 a of the eccentric sleeves 25 and supported thereby, is designed to displace by a required quantity with respect to the axis C₂ of the eccentric sleeves 25, as shown in FIG. 2, and is also designed to be displaced by rotating the eccentric sleeves 25 in the positive or negative direction by a mechanism to be described later.

[0034] A pair of adjusting shafts 28 are rotatably supported to oppose the eccentric sleeves 25 and to be orthogonal to the roll shafts 26 at positions outer than the location of the roll shafts 26 in the first stand 16 (positions farther from the opposing sides of the rolling machines 12 and 13). Each adjusting shaft 28 has a pair of adjusting worms 29 fitted thereon to oppose the eccentric sleeves respectively and to be rotatable integrally with the shaft 28, as shown in FIG. 2. Each adjusting worm 29 is designed to mesh with teeth 25 b formed on the periphery of the associated eccentric sleeve 25. These two adjusting worms 29 fitted to each adjusting shaft 28 are designed to have opposite directions of helix, while the adjusting worms 29 opposing the eccentric sleeves 25 fitted on the same roll shaft 26 are designed to be of the same direction of helilx. Meanwhile, the adjusting shafts 28 each have at a shaft end an operating worm wheel 30 to be rotatable integrally therewith. These operating worm wheel 30 are meshed respectively with associated operating worms 32 fitted on an operating shaft 31 pivotally supported in the first stand 16. More specifically, if the operating shaft 31 is rotated in the positive or negative direction by suitable driving means such as a motor, the pair of adjusting shafts 28 rotate in the same direction to rotate the eccentric sleeves 25 through the associated adjusting worms 29, respectively. Thus, the center distance between the roll shafts 26 each supported by a pair of eccentric sleeves 25 is changed, achieving adjustment of the clearance between the opposing first rolls 17.

[0035] As described above, in the first rolling machine 12 employing the screw down device utilizing eccentric sleeves 25, the inner side of the first stand 16 (the side toward which the roll shafts 26 displace) is designed to have an extremely small thickness, as shown in FIG. 1. Meanwhile, in the second rolling machine 13, the roll shafts 26 are also located eccentrically toward the inner side of the second stand 18, and thus the inner side of the second stand 18 is designed to have an extremely small thickness. The first rolling machine 12 and the second rolling machine 13 are disposed adjacent to each other such that the inner sides each designed to have a small wall thickness oppose each other, so that the center distance P between the rolls 17 in the first rolling machine 12 and the rolls 19 in the second rolling machine 13 can be preset to be not more than 1.5 times the diameter R of the rolls 17(19).

[0036] Next, driving systems for the first rolling machine 12 and second rolling machine 13 will be described. As shown in FIG. 3, a horizontal first drive shaft 33 is supported rotatably on the lower left side with respect to the workpiece pass line PL to extend orthogonal to the line PL. A first transmission shaft 35 rotatably supported in a first gearbox 34 is connected, through a first coupling 36, to the first drive shaft 33 at the distal end with respect to the pass line PL, as shown in FIG. 5. Meanwhile, a first speed-reducing gear 37 is attached to the first transmission shaft 35 to be rotatable integrally therewith. This gear 37 is meshed with a first drive gear 39 attached to an output shaft 38 a of a first drive motor 38 to be rotatable integrally therewith. The motor 38 can rotate in the positive and negative directions. Thus, if the first drive motor 38 is driven, the first drive shaft 33 is rotated in a required direction through the first drive gear 39, the first speed-reducing gear 37 and the first transmission shaft 35.

[0037] A first intermediate shaft 40 inclined at an angle of 45° with respect to the first drive shaft 33 is supported above it rotatably in the housing 15, and a first intermediate bevel gear 41 attached to one end of the shaft 40 to be rotatable integrally therewith is meshed with a first bevel gear 42 attached to the first drive shaft 33 to be rotatable integrally therewith. Further, a pair of first roll shafts 43 are rotatably supported in the housing 15 to be parallel to the first intermediate shaft 40 (at an inclination angle of 45° with respect to the horizontal plane). A first connecting gear 44 fitted to one roll shaft 43 to be rotatable integrally therewith is meshed with a first driven gear 45 attached to the first intermediate shaft 40 to be rotatable integrally therewith. Further, those ends of the first roll shafts 43 that are directed to the pass line PL are connected to the roll shafts 26 of the first rolls 17 in the first rolling machine 12 through first spline shaft couplings 46 to be shiftable in the axial directions, respectively. Here, the pair of first roll shafts 43 are meshed with the associated first connecting gears 44 respectively so as to be rotated in opposite directions with respect to each other. That is, when the first drive shaft 33 is rotated by the first drive motor 38 in a required direction, the pair of first roll shafts 43 are rotated through the first bevel gear 42, the first intermediate bevel gear 41, the first driven gear 45 and the first connecting gears 44 in opposite directions with respect to each other. This rotates the first rolls 17 of the first rolling machine 12 opposing each other across the pass line PL in opposite directions with respect to each other. Meanwhile, as described above, even if the first stand 16 is shifted in a direction orthogonal to the pass line PL, the first spline shaft couplings 46 are adapted to achieve transmission of power to the first rolls 17.

[0038] As shown in FIG. 4, a horizontal second drive shaft 47 is supported rotatably on the lower right side with respect to the workpiece pass line PL to be orthogonal to the line PL. A second transmission shaft 49 rotatably supported in a second gearbox 48 is connected, through a second coupling 50, to the second drive shaft 47 at the distal end with respect to the pass line PL, as shown in FIG. 5. Meanwhile, a second speed-reducing gear 51 is attached to the second transmission shaft 49 to be rotatable integrally therewith. This gear 51 is meshed with a second drive gear 53 attached to an output shaft 52 a of a second drive motor 52 to rotate integrally therewith. The motor 52 can rotate in the positive and negative directions. Thus, if the second drive motor 52 is driven, the second drive shaft 47 is rotated in the same direction as the first drive shaft 33 through the second drive gear 53, the second speed-reducing gear 51 and the second transmission shaft 49.

[0039] A second intermediate shaft 54 inclined at an angle of 45° with respect to the second drive shaft 47 is supported above it rotatably in the housing 15, and a second intermediate bevel gear 55 attached to one end of the shaft 54 to be rotatable integrally therewith is meshed with a second bevel gear 56 attached to the second drive shaft 47 to be rotatable integrally therewith. Further, a pair of second roll shafts 57 are rotatably supported in the housing 15 to be parallel to the second intermediate shaft 54 (at an inclination angle of 45° with respect to the horizontal plane). A second connecting gear 58 is fitted to one roll shaft 57 to be rotatable integrally therewith. The second connecting gear 58 is meshed with a second driven gear 59 attached to the second intermediate shaft 54 to be rotatable integrally therewith.

[0040] Further, those ends of the second roll shafts 57 that are directed to the pass line PL are connected to the roll shafts 26 of the second rolls 19 through second spline shaft couplings 60 to be shiftable in the axial directions, respectively. Here, the pair of second roll shafts 57 are meshed respectively with the second connecting gears 58 so as to be rotated in opposite directions with respect to each other. That is, when the second drive shaft 47 is rotated by the second drive motor 52 in the same direction as the first drive shaft 33, the pair of second roll shafts 57 are rotated through the second bevel gear 56, the second intermediate bevel gear 55, the second driven gear 59 and the second connecting gears 58 in opposite directions with respect to each other. This rotates the pair of second rolls 19 of the second rolling machine 13 opposing each other across the pass line PL in opposite directions with respect to each other. Meanwhile, even if the second stand 18 is shifted in a direction orthogonal to the pass line PL, as described above, the second spline shaft couplings 60 are adapted to achieve transmission of power to the second rolls 19.

[0041] Here, rotation of the first drive motor 38 and that of the second drive motor 52 are controlled to be reversed each time a workpiece 11 passes through the rolling mill 10, and also the rotational speed of the rolling machine 12 or 13 located on the feed-out side is controlled to be higher than that of the rolling machine 13 or 12 located on the feed-in side, achieving smooth rolling of the workpiece 11.

[0042] Operation of the Embodiment

[0043] Operation of the reversible guideless rolling mill according to the above constitution will now be described. First, in the first rolling machine 12 and the second rolling machine 13, the clearance between the first rolls 17 and the clearance between the second rolls 19 are adjusted by the screw down devices respectively depending on the cross-sectional profile of a workpiece 11 to be rolled. Further, the first stand 16 and the second stand 18 are shifted and postioned by the hydraulic cylinders 20 and 22, respectively, so that a predetermined position of first dual-purpose rolling pass 21 designed to serve as an oval caliper of the first rolls 17 in the first rolling machine 12 is aligned with the pass line PL and that a predetermined position of second dual-purpose rolling pass 23 designed to serve as a round caliper of the second rolls 19 in the second rolling machine 13 is aligned with the pass line PL.

[0044] In this state, when a workpiece 11 loaded on the roller table 14 located on the outer side (farther side from the second rolling machine 13) of the first rolling machine 12 is rolled by passing it through the first dual-purpose rolling pass 21 defined between the first rolls 17, the workpiece 11 is rolled to have an oval cross-sectional profile. The front end portion of the workpiece 11 still nipped between the first rolls 17 is fed to and passed successively through the second dual-purpose caliber 23 of the second rolls 19 to be rolled to have a round cross-sectional profile. Here, since the center distance P between the rolls 17 of the first rolling machine 12 and the rolls 19 of the second rolling machine 13 is designed to be not more than 1.5 times the diameter R of these rolls 17(19), the workpiece 11 can be fed accurately to the second dual-purpose caliber 23 of the second rolling machine 13 without interposing a holding guide between these two rolling machines 12 and 13. In addition, the first rolls 17 in the first rolling machine 12 also serve as a holding guide for the workpiece 11 to prevent effectively twisting or the like of the workpiece 11.

[0045] Since the rotational axes of the first rolls 17 in the first rolling machine 12 and those of the second rolls 19 in the second rolling machine 13 are all inclined by an angle of 45° with respect to the horizontal plane, the height of the workpiece pass line PL from the base plane on which the rolling mill 10 is installed can be reduced to reduce the depth from the floor of a plant to the base plane, achieving reduction in the cost of foundation work etc.

[0046] When the workpiece 11 rolled to have a round cross section is fed out from the second rolling machine 13 onto the opposite side roller table 14, the second stand 18 is shifted by the second hydraulic cylinders 22 by a predetermined pitch to align the center of another predetermined position of dual-purpose caliber 23 designed to serve as an oval caliber with the pass line PL. Meanwhile, in the first rolling machine 12, the first stand 16 is shifted by a predetermined pitch by the first hydraulic cylinders 20 to align the center of another predetermined position of dual-purpose caliber 21 designed to serve as a round caliber with the pass line PL. Thus, after the stands 16 and 18 are shifted correlatively, the workpiece 11 is fed from the rear end through the second dual-purpose caliber 23 of the second rolls 19 and is rolled to have an oval cross section. The thus treated workpiece 11 is then passed successively through the first dual-purpose caliber 21 of the first rolls 17 and is rolled to have a round cross section. Here again, the workpiece 11 is fed accurately to the first dual-purpose caliber 21 of the first rolling machine 12, and also twisting or the like of the workpiece 11 can be prevented effectively.

[0047] As described above, the workpiece 11 is rolled to have a desired cross section by reciprocating the workpiece 11 under shifting of the stands 16 and 18 correlatively every time the workpiece 11 is passed through the rolling machines 12 and 13. Here, the workpiece 11 need not be passed through all of the dual-purpose calibers 21 and 23 in the rolling machines 12 and 13 but are passed through the calibers 21 and 23 according to a predetermined pattern that are necessary to obtain the desired cross section.

[0048] Next, when the diameter or the like of the workpiece 11 is changed on an order change, the operating shafts 31 of the screw down devices of the rolling machines 12 and 13 are turned in the required directions by motors or the like, respectively. Thus, the eccentric sleeves 25 are turned to change the clearance between the rolls 17 and that between the rolls 19. That is, the dual-purpose calibers 21 and 23 of the rolling machines 12 and 13 are preset to function as oval calibers and round calibers respectively according to the new order for the workpiece 11, and a workpiece 11 of the new order is reciprocated with respect to the rolling mill 10 under shifting of the stands 16 and 18 based on a predetermined pattern, thus rolling the workpiece 11 to have a predetermined cross section. It should be noted here that the roll passes defined between the first rolls 17 and those between the second rolls 19 are dual-purpose calibers that can be utilized both as oval calibers and round calibers, so that a single set of rolls can roll workpieces 11 over a wide size range, and a few sets of rolls can cover a wider size range.

[0049] Since the rolls 17 and the rolls 19 are arranged adjacent to each other on the upstream side and downstream side along the pass line at a center distance P of not more than 1.5 times the roll diameter, workpieces 11 can be rolled accurately in the absence of holding guide for it. In other words, intricate operations of adjusting and inspecting the holding guide involved in order changes can be eliminated, so that the time loss associated with order changes can be reduced to improve manufacturing efficiency. Further, there occurs no defective products attributed to the presence of holding guide, and the total length of the rolling mill can be reduced to enable effective utilization of the space in a plant.

[0050] In the embodiment described above, while the calibers defined between the rolls 17 and those between the rolls 19 are dual-purpose calibers which can be utilized both as oval calibers and round calibers, they are not limited to the dual-purpose calibers. For example, a predetermined number of oval calibers 61 a and a predetermined number of round calibers 61 b may be formed alternately on the first rolls 17 to be arranged in the axial direction as shown in FIG. 7(a), whereas a predetermined number of round calibers 62 b and a predetermined number of oval calibers 62 a may be formed alternately on the second rolls 19 to be arranged in the axial direction as shown in FIG. 7(b). In this example, the inside diameters of the calibers to be defined between the rolls 17(19) are designed to be reduced gradually from one side toward the other side of the rolls in the axial directions. Thus, a workpiece 11 can be rolled to a predetermined cross-sectional profile by passing it through oval calibers 61 a(62 a) and the round calibers 61 b(62 b) alternately. It should be noted here that in the advancing stroke and retracting stroke of the workpiece 11, if the caliber through which the workpiece 11 is passed first and the caliber through which the workpiece 11 is passed next are designed to be an oval caliber 61 a(62 a) and a round caliber 61 b(62 b), respectively, the feeding direction of the workpiece 11 having passed through the rolling mill 10 need not be inverted, but the workpiece 11 is designed to be fed back as such to the rolling machines 13 and 12 in the rolling mill 10 without turning the workpiece 11 in the radial direction.

[0051] Meanwhile, there may also be employed first rolls 17 having rhombic-square calibers, i.e., a predetermined number of rhombic calibers 63 a and a predetermined number of square calibers 63 b may be formed alternately on the first rolls 17 to be arranged in the axial direction as shown in FIG. 8(a), whereas a predetermined number of square calibers 64 b and a predetermined number of rhombic calibers 64 a may be formed alternately on the second rolls 19 to be arranged in the axial direction as shown in FIG. 8(b). In the case where rhombic-square calibers are employed, if a workpiece is designed to be passed finally through a square caliber, the workpiece need not be turned axially for the next pass, and the mechanism can be simplified.

[0052] The number of calibers to be defined between each pair of rolls is not limited to the above embodiment. The driving means for shifting the rolls are not limited to the hydraulic cylinders as used in the embodiment, but other mechanisms such as a combination of a motor and a screw nut can be employed. Further, the reference based on which the tilting posture of the rolls with respect to the horizontal plane is set may be the rotational axes of the second rolls in the second rolling machine. Incidentally, the rotational axes of the first rolls in the first rolling machine (one rolling machine) and those of the second rolls in the second rolling machine (the other rolling machine) may not necessarily be displaced from each other by 90°0 but by a nearly right angle.

[0053] Next, an embodiment of a line of guideless rolling machines according to another aspect of the present invention will be described. In the prior art, a pass schedule for workpieces including steel bars and wire rods are roughly divided generally into rough rolling through a line of rough rolling machines, intermediate rolling through a line of intermediate rolling machines and finish rolling through a line of finish rolling machines. A workpiece heated to a required temperature is rolled to a required cross-sectional dimension through the line of rough rolling machines and the line of intermediate rolling machines and then rolled to a desired final cross-sectional dimension (a cross-sectional profile) through the line of finish rolling machines. Taking the line of intermediate rolling machines for example, a plurality of rolling machines are arranged in series at predetermined intervals in alignment with a pass line along which a workpiece is fed, and thus the workpiece is passed through the rolling machines to be rolled down to a predetermined dimension to be acceptable by the line of finish rolling machines.

[0054] Each rolling machine has a pair of rolls rotatably supported in a housing, and a workpiece is designed to undergo a required rolling treatment by passing through rolling passes (calibers) defined between the rolls. The drawing or rolling in the line of intermediate rolling machines, rolling passes of oval-round system having oval calibers and round calibers arranged alternately and those of rhombic-square system having rhombic calibers and square calibers arranged alternately are employed strategically.

[0055] In the oval-round system, a holding guide composed essentially of rollers, which is disposed on the inlet side of a round caliber, guides a workpiece rolled through an oval caliber in an accurate orientation into a round caliber so as to achieve accurate rolling. Meanwhile, in the case of the rhombic-square system, a like holding guide is disposed on the inlet side of a square caliber so as to ensure high reduction of area.

[0056] Further, it is essential to install, in each rolling machine, a screw down device for adjusting the clearance between the opposing rolls so as to change the cross-sectional dimension of the workpiece. This screw down device is designed to bring one roll closer to or farther from the other roll which is fixed in a certain position. In other words, a stand supporting rotatably one roll is shiftably incorporated into a housing, and the stand is shifted using a suitable driving mechanism to adjust the roll clearance.

[0057] However, when the clearance between the rolls is adjusted by the screw down device incorporated into the rolling machine, the holding guide disposed in the rolling machine needs adjustment to a proper position accordingly, so that a longer time is required for adjustment in accordance with order changes and the like, disadvantageously. Since guiding failure of the holding guide leads to defective rolled products, it is essential to carry out frequently maintenance of bearings, inspection of roll surface flaws, inspection of rotation of the rolls, etc. It can also be pointed out that the holding guide interposed between the rolling machines makes the structure of the machine complicated and requires an extra cost of equipment.

[0058] Further, since the temperature of the workpiece rises greatly due to rolling deformation when rolling is performed at a high speed, it is practiced to cool the workpiece through a water-cooled trough or the like on the outlet side of the rolling machine so as to control temperature rise. It can also be pointed out here that when the workpiece rolled in the rolling machine has an oval cross-sectional profile, the workpiece undergoes biased cooling due to its shape, so that cooling through a water-cooled trough cannot be utilized, and the workpiece cannot be cooled sufficiently.

[0059]FIG. 9 shows schematic constitution of a line of guideless rolling machines according to the embodiment. A plurality of rolling mills 110 (six rolling mills in the embodiment) are arranged at predetermined intervals in alignment with a pass line PL along which a workpiece 111 is fed. Each rolling mill 110 has a first rolling machine 113 and a second rolling machine 115 arranged in series. The first rolling machine 113 is located on the upstream side (rear side with respect to the machine direction) and contains rotatably a pair of first rolls 112 opposing each other across the pass line PL, and the second rolling machine 115 is located on the downstream side (front side with respect to the machine direction) and contains rotatably a pair of second rolls 114 also opposing each other across the pass line PL. The rotational axes of the first rolls 112 in the first rolling machine 113 displace at an angle of 90° from those of the second rolls 114 in the second rolling machine 115, and the first rolls 112 and the second rolls 114 are oriented such that the rotational axes of the former and those of the latter are inclined at an angle of 45° with respect to the horizontal plane respectively (X orientation). Be noted here, on the basis, for example, of the first rolls 112 disposed in the first rolling machine 113 located on the upstream side with respect to the machine direction along which the workpiece 111 is fed, while the inclination angle of the rotational axis of each roll 112 with respect to the horizontal plane is not limited to 45° but may be within the range of 20° to 90°, it is most preferably 45°.

[0060] As shown in FIG. 12 or 13, the first rolls 112 of the first rolling machine 113 define therebetween an oval caliber 116 and a round caliber 117 as rolling passes with an interval being secured between them in the axial direction, while the second rolls 114 of the second rolling machine 115 define an oval caliber 116 and a round caliber 117 as rolling passes with an interval being secured between them in the axial direction. In this embodiment, the oval caliber 116 in the first rolling machine 113 and the round caliber 117 in the second rolling machine 115 are positioned in alignment with the pass line PL, and a workpiece 111 passed through the rolling mill 110 is designed to have a round cross-sectional profile. It should be noted here that stands 120 (to be described later) in which the rolls 112 and 114 of the first and second rolling machines 113 and 115 are disposed are designed to be removable with respect to the housing 119 of the rolling mill 110, respectively. The stands 120 located on the upstream side and on the downstream side respectively are counterchanged to bring the other oval caliber 116 or the other round caliber 117 in alignment with the pass line PL, and thus the workpiece 111 is adapted to be rolled through other calibers. In this case, however, the downstream-side rolling pass is designed to be a round caliber 117.

[0061] The center distance P between the first rolls 112 in the first rolling machine 113 and the second rolls 114 in the second rolling machine 115 is preset to be not more than 1.2 times the diameter R of the rolls 112(114), as shown in FIG. 10. By reducing the center distance P between the pair of rolls 112 and the pair of rolls 114 arranged adjacent to each other along the pass line as described above, the workpiece 111 rolled first through the oval caliber 116 in the first rolling machine 113 can be guided accurately to the round caliber 117 in the second rolling machine 115 even in the absence of workpiece holding guide. That is, operations of adjustment and inspection of the holding guide required in accordance with an order change can be omitted, and occurrence of defective products attributed to the presence of holding guide can be eliminated. Further, the absence of the holding guide can reduce the total length of the line of rolling machines. A water-cooled trough 118 is located as cooling means on the outlet side of each rolling mill 110, so that the workpiece 111 rolled through each rolling mill 110 to have an increased temperature is cooled through the trough 118 (temperature control) to maintain the workpiece 111 at a temperature suitable for the rolling treatment in the next rolling mill 110.

[0062] It should be noted here that the center distance P between the opposing rolls 112 and 114 can be reduced by employing a mechanism (to be described later) as a screw down device for adjusting the clearance between the opposing rolls 112(114) of the rolling machines 113(115). Therefore, the constitutions of the rolling machines 113 and 115 will be described. Here, since the first rolling machine 113 and the second rolling machine 115 are of the same constitution, except that the rotational axes of the rolls 112 displace by an angle of 90° from those of the rolls 114, the constitution of the first rolling machine 113 only will be described. The same elements in the second rolling machine 115 as in the first rolling machine 113 are affixed with the same reference numbers respectively, and detailed description of them will be omitted.

[0063] The stand 120 disposed in the housing 119 of the rolling mill 110 contains two pairs of through holes 120 a defined in a direction orthogonal to the pass line PL, each pair containing an upper through hole 120 a and a lower through hole 120 a, as shown in FIG. 10. That is, four through holes 120 a are defined in the first stand at inner positions (closer to the downstream side) on each side of the workpiece pass line PL and at an upper position and a lower position, respectively. An eccentric sleeve 121 is fitted rotatably in each through hole 120 a, and each sleeve 121 contains an eccentric through hole 121 a having an axis offset from that of the through hole 120 a. A roll shaft 122 is inserted to the upper and lower eccentric through holes 121 a and are rotatably born thereby through bearings 123. Meanwhile, the roll shaft 122 has the first roll 112 fitted thereon between the eccentric sleeves 121 to be rotatable integrally with the shaft 122. A workpiece 111 is designed to be rolled by passing it through an oval caliber 116 defined between the pair of first rolls 112 arranged in a diagonally vertical relationship. The axis C₁ of each roll shaft 122, inserted to the eccentric through holes 121 a of the eccentric sleeves 121 and supported thereby, is designed to displace by a required quantity with respect to the axis C₂ of the eccentric sleeves 121, as shown clearly in FIG. 11, and is also designed to be displaced by rotating the eccentric sleeves 121 in the positive or negative direction by a mechanism to be described later.

[0064] A pair of adjusting shafts 124 are rotatably supported to oppose the eccentric sleeves 121 fitted on the upper and lower portions of the roll shafts 122 and to be orthogonal to the roll shafts 122 on the upstream side of the roll shafts 122 in the stand 120. Each adjusting shaft 124 has a pair of adjusting worms 125 fitted thereon to oppose the eccentric sleeves respectively and to be rotatable integrally with the shaft 124, as shown in FIG. 11. Each adjusting worm 125 is designed to mesh with teeth 121 b formed on the periphery of the associated eccentric sleeve 121. These two adjusting worms 125 fitted to each adjusting shaft 124 are designed to have opposite directions of helix, while the adjusting worms 125 opposing the eccentric sleeves 121 fitted on the same roll shaft 122 are designed to be of the same direction of helilx. Meanwhile, the adjusting shafts 124 each have at a shaft end an operating worm wheel 126 to be rotatable integrally therewith. These operating worm wheels 126 are meshed respectively with associated operating worms 128 fitted on an operating shaft 127 rotatably supported in the stand 120. More specifically, if the operating shaft 127 is rotated in the positive or negative direction by suitable driving means such as a motor, the pair of adjusting shafts 124 rotate in the same direction to rotate the associated eccentric sleeves 121 through the adjusting worms 125, respectively. Thus, the center distance between the roll shafts 122 each supported by a pair of eccentric sleeves 121 is changed, achieving adjustment of the clearance between the opposing first rolls 112.

[0065] As described above, in the first rolling machine 113 employing the screw down device utilizing eccentric sleeves 121, the downstream side of the stand 120 (the side toward which the roll shafts 122 displace) is designed to have an extremely small thickness, as shown in FIG. 10. Meanwhile, in the second rolling machine 115, the roll shafts 122 are located eccentrically toward the upstream side of the stand 120, and thus the upstream side of the stand 120 is designed to have an extremely small thickness. The first rolling machine 113 and the second rolling machine 115 are disposed adjacent to each other such that the inner sides each designed to have a small wall thickness oppose each other, so that the center distance P between the rolls 112 in the first rolling machine 113 and the rolls 114 in the second rolling machines 115 can be preset to be not more than 1.2 times the diameter R of the rolls 112(114).

[0066] The first rolls 112 in the first rolling machine 113 and the second rolls 114 in the second rolling machine 115 constituting the rolling mill 110 are designed to be driven by a single drive motor 129, as shown in FIGS. 12 to 14. Here, each rolling mill 110 is designed to achieve 2-pass reduction of area in the range of 25% to 40%.

[0067] As shown in FIG. 12, a horizontal first drive shaft 130 is supported rotatably on the lower left side with respect to the workpiece pass line PL to extend orthogonal to the line PL. A first transmission shaft 132 rotatably supported in a gearbox 131 is connected, through a first coupling 133, to the first drive shaft 130 at the distal end with respect to the pass line PL, as shown in FIG. 14. Meanwhile, a first speed-reducing gear 134 is attached to the first transmission shaft 132 to be rotatable integrally therewith. This gear 134 is meshed with a drive gear 135 attached to an output shaft 129 a of a drive motor 129 to be rotatable integrally therewith. Thus, if the drive motor 129 is driven, the first drive shaft 130 is rotated in a required direction through the drive gear 135, the first speed-reducing gear 134 and the first transmission shaft 132.

[0068] A first intermediate shaft 136 inclined at an angle of 45° with respect to the first drive shaft 130 is supported above it rotatably in the housing 119, and a first intermediate bevel gear 137 attached to one end of the shaft 136 to be rotatable integrally therewith is meshed with a first bevel gear 138 attached to the first drive shaft 130 to be rotatable integrally therewith. Further, a pair of first roll shafts 139 are rotatably supported in the housing 119 to be parallel to the first intermediate shaft 136 (at an inclination angle of 45° with respect to the horizontal plane). A first connecting gear 140 fitted to one roll shaft 139 to be rotatable integrally therewith is meshed with a first driven gear 141 attached to the first intermediate shaft 136 to be rotatable integrally therewith. Further, those ends of the first roll shafts 139 that direct to the pass line PL are connected to the roll shafts 122 of the first rolls 112 in the first rolling machine 113 through a first detaching coupling 142 to be shiftable in the axial directions, respectively. Here, the pair of first roll shafts 139 are meshed with the associated first connecting gears 140 respectively so as to be rotated in opposite directions with respect to each other. That is, when the first drive motor 129 rotates the first drive shaft 130 in a required direction, the pair of first roll shafts 139 are rotated through the first bevel gear 138, the first intermediate bevel gear 137, the first driven gear 141 and the first connecting gears 140 in opposite directions with respect to each other. This rotates the pair of first rolls 112 of the first rolling machine 113 opposing each other across the pass line PL in opposite directions with respect to each other.

[0069] A long shaft 143 extended parallel to the first drive shaft 130 below and across the pass line PL is rotatably supported. A second transmission shaft 144 rotatably supported in the gearbox 131 is connected to the left end of the long shaft 143 through a second coupling 145. Further, a second transmission gear 146 is attached to the second transmission shaft 144 to be rotatable integrally therewith. The second transmission gear 146 is meshed with a first transmission gear 147 attached to the first transmission shaft 132 to be rotatable integrally therewith. Thus, the long shaft 143 is rotated in the opposite direction as the first drive shaft 130 by driving the drive motor 129.

[0070] A second drive shaft 148 is rotatably supported in the housing 119 on the lower right side with respect to the pass line PL to oppose the first drive shaft 130, as shown in FIG. 13. A driven intermediate gear 149 attached to the second drive shaft 148 to be rotatable integrally therewith is meshed with a drive intermediate gear 150 attached to the long shaft 143 to be rotatable integrally therewith, so that the second drive shaft 148 rotates in the same direction as the first drive shaft 130. A second intermediate shaft 151 inclined at an angle of 45° with respect to the second drive shaft 148 is supported above it rotatably in the housing 119, and a second intermediate bevel gear 152 attached to one end of the shaft 151 to be rotatable integrally therewith is meshed with a second bevel gear 153 attached to the horizontal second drive shaft 148 to be rotatable integrally therewith. Further, a pair of second roll shafts 154 are rotatably supported in the housing 119 to be parallel to the second intermediate shaft 151 (tilted at an inclination angle of 45° with respect to the horizontal plane). A second connecting gear 155 attached to one roll shaft 154 to be rotatable integrally therewith is meshed with a second driven gear 156 attached to the second intermediate shaft 151 to be rotatable integrally therewith.

[0071] Further, that end of one second roll shaft 154 directed to the pass line PL is connected detachably to the roll shaft 122 of one second roll 114 in the second rolling machine 115 through a second detaching coupling 157. Meanwhile, that end of the other second roll shaft 154 directed to the pass line PL is connected detachably to the roll shaft 122 of the other second roll 114 in the second rolling machine 115 through a second detaching coupling 157. Here, the pair of second roll shafts 154 are designed to be rotated in opposite directions with respect to each other under engagement between the second connecting gears 155. That is, when the second drive shaft 148 is rotated by the drive motor 129 through the long shaft 143 in the same direction as the first drive shaft 130, the pair of second roll shafts 154 are rotated through the second bevel gear 153, the second intermediate bevel gear 152, the second driven gear 156 and the second connecting gears 155 in opposite directions with respect to each other. This rotates the pair of second rolls 114 of the second rolling machine 115 opposing each other across the pass line PL in opposite directions with respect to each other.

[0072] Next, operation of the line of guideless rolling mills according to the above constitution will be described. A workpiece 111 having a required cross-sectional dimension is introduced to a first rolling machine 113 of a first rolling mill 110 located at the most upstream position, as shown in FIG. 9, and is subjected to a required rolling treatment by passing through an oval caliber 116 defined between a pair of opposing first rolls 112 of the rolling machine 113. The thus treated workpiece 111 is supplied successively to between a pair of second rolls 114 of a second rolling machine 115 and is subjected to a required rolling treatment by passing through a round caliber 117 defined between the second rolls 114. Here, the center distance P between the rolls 112 of the first rolling machine 113 and the rolls 114 of the second rolling machine 115 is designed to be not more than 1.2 times the diameter of these rolls 112(114), the workpiece 111 can be supplied accurately to a round caliber 117 of the second rolling machine 115 in the absence of holding guide. In addition, the first rolls 112 in the first rolling machine 113 also serve as a workpiece holding guide to prevent effectively twisting or the like of the workpiece 111.

[0073] Since the rotational axes of the first rolls 112 in the first rolling machine 113 and those of the second rolls 114 in the second rolling machine 115 are all inclined by an angle of 45° with respect to the horizontal plane, the height of the workpiece pass line PL from the base plane on which the rolling mill 110 is installed can be reduced to reduce the depth from the floor of a plant to the base plane, achieving reduction in the cost of foundation work etc.

[0074] The workpiece 111 having passed through the first rolling mill 110 is cooled while it passes through a water-cooled trough 118, as shown in FIG. 9, to such a temperature as is suitable for rolling and then introduced to a second rolling mill 110 for another required rolling treatment. Subsequently, the workpiece 111 is fed downstream under rolling treatments by rolling mills 110 and cooling by water-cooled troughs 118 which are repeated alternately in the same manner as described above until it has a required cross-sectional dimension. More specifically, since the workpiece 111 fed out from each rolling mill 110 has a round cross-sectional profile, the workpiece 111 can be cooled efficiently through a water-cooled trough 118 located on the outlet side of each rolling mill 110 to control temperature rise attributed to rolling deformation, even when workpieces 111 are rolled at high rates, and thus rolling treatments can be carried out while the workpieces 111 are maintained constantly at proper temperatures.

[0075] Next, when the diameter or the like of the workpiece 111 is changed on an order change, the operating shafts 127 of the screw down devices of the rolling machines 113 and 115 are turned in the required directions by motors or the like, respectively. Thus, the eccentric sleeves 121 are turned to change the clearance between the rolls 112 and that between the rolls 114. Therefore, if a workpiece 111 of the new order is supplied to the rolling mill 110, a required rolling treatment is applied to the workpiece 111 by the pairs of opposing rolls 112 and 114.

[0076] Use of rolling mills 110 each having a pair of rolls 112 and a pair of rolls 114 arranged adjacent to each other on the upstream side and downstream side along the workpiece pass line at a center distance P of not more than 1.2 times the roll diameter can constitute a line of rolling machines in the absence of workpiece holding guide. In other words, intricate operations of adjusting and inspecting the holding guide involved in order changes can be eliminated, so that the time loss associated with order changes can be reduced to improve manufacturing efficiency. Further, there occurs no defective products attributed to the presence of holding guide, and the total length of the line of rolling mills can be reduced to enable effective utilization of the space in a plant.

[0077] Be noted here that the embodiment described above is of the case where each pair of rolls define two calibers therebetween. However, the number of calibers may be one or more than 2. The pair of rolling machines constituting each rolling mill may be adapted to be driven respectively by independent drive motors. Further, the cooling means may not be limited to the water-cooled troughs as illustrated in the embodiment, but other cooling means may be employed. Furthermore, the line of guideless rolling machines can be applied to all of the line of rough rolling machines, that of intermediate rolling machines and that of finishing rolling machines. The reference based on which the tilting posture of the rolls with respect to the horizontal plane is set may be the rotational axes of the rolls in the downstream (second) rolling machine. The rotational axes of the first rolls in the first rolling machine (one rolling machine) and those of the second rolls in the second rolling machine (the other rolling machine) may not necessarily be displaced from each other by 90° but by a nearly right angle.

[0078] In short, the line of guideless rolling mills according to the second aspect of the present invention is as follows.

[0079] A plurality of rolling mills 110 are arranged in alignment with a pass line PL along which a workpiece 111 is fed. Each rolling mill 110 contains a pair of rolling machines 113 and 115 arranged on the upstream side and downstream side with respect to the pass line. Each rolling machine 113(115) has a pair of rolls 112(114). Said two rolling machines 113 and 115 are arranged at a center distance P between the rolls 112 and 114 is not more than 1.2 times the roll diameter. The rotational axes of the rolls in one rolling machine 113 are displaced by almost right angle from those of the rolls 114 in the other rolling machine 115, and the rotational axes of the rolls 112 in one rolling machine 113 serving as a reference are inclined by an angle of 20° to 90° with respect to the horizontal plane. The rolling machine 115, in the rolling mill 110, located on the downstream side with respect to the pass line along which a workpiece 111 is fed is designed to define a round caliber 117 so as to roll a workpiece 11 into a round cross-sectional profile. Cooling means 118 is disposed on the outlet side of each rolling mill 110.

[0080] As described above, according to the reversible guideless rolling mill of the present invention, since a short roll center distance is secured between one rolling machine and the other rolling machine, rolling of workpieces can be achieved smoothly in the absence of workpiece holding guide. That is, the absence of workpiece holding guide achieves simplification of the structure of the rolling mill and reduction of the entire length of the mill, achieving cost saving. Besides, occurrence of defective product attributed to the presence of holding guide can be eliminated, and operations of adjustment and inspection in accordance with order changes can be omitted, advantageously.

[0081] Since rolls in each rolling machine are designed to define calibers which can be utilized both as oval calibers and round calibers, a single set of rolls can roll workpieces 11 over a wide size range, and a few sets of rolls can cover a wider size range. Thus, storage management of rolls can be simplified, and equipment cost can be reduced.

[0082] Meanwhile, in the line of guideless rolling machines according to the other aspect of the present invention, use of rolling mills each having two pairs of rolls arranged adjacent to each other in alignment with the workpiece pass line at a short center distance can facilitate rolling of workpieces in the absence of holding guide. In other words, workpiece holding guides are dispensed with to achieve simplification of the structure of the rolling mill and also reduction of the total length of the line of the rolling mills, thus saving cost. Besides, occurrence of defective products attributed to the presence of holding guide can be obviated, and time-consuming adjusting operations and intricate inspecting operations involved in order changes can be eliminated, advantageously.

[0083] Besides, since the workpiece fed out from each rolling mill is designed to have a round cross-sectional profile, and since cooling means is disposed on the outlet side of each rolling mill, the workpiece can be cooled evenly to an appropriate temperature (prevention of temperature rise) without biased cooling.

[0084] It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention.

[0085] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims. 

What is claimed is:
 1. A reversible guideless rolling mill for rolling a workpiece to be rolled into a required cross-sectional profile while the workpiece is reciprocated along a pass line; wherein two rolling machines each having a pair of rolls which defines a plurality of calibers in axial direction for rolling said workpiece are arranged in series along said pass line of the workpiece so as to establish a center distance between the rolls in one rolling machine and the rolls in the other rolling machine to be no more than 1.5 times a roll diameter; rotational axes of the rolls in one rolling machine are displaced by almost right angle from that of the rolls in the other rolling machine; and the rolls in said two rolling machines are designed to be shifted in crossing directions to the pass line of the workpiece so that each caliber is aligned with said pass line.
 2. The reversible guideless rolling mill according to claim 1, wherein the rotational axes of the rolls in the other rolling machine as standard are in designed to incline at an angle of 20° to 90° with respect to a horizontal plane.
 3. The reversible guideless rolling mill according to claim 1 or 2, wherein the calibers are designed to be able to serve both as oval calibers and round calibers by adjusting a clearance between the pair of rolls in each rolling machine. 